Properlly fallback to pixman, by appending it to WESTONBACKEND for kms only, as when --use-pixman is passed to fb-backend it fails with invalid argument
Change filename of pixman session, so it appears second in the alphebetical list

git-svn-id: https://rebeccablackos.svn.sourceforge.net/svnroot/rebeccablackos@2478 56e3d1a8-0179-4092-b3e2-9fbbcda0c0a9